Hydraulically actuated die clamps are employed to hold down the periphery of die plates on flat bolster plates, provided with T-slot anchorage, in order to achieve high clamping forces. Prior art clamping devices are disclosed in U.S. Pat. Nos. 4,511,127 dated Apr. 16, 1985 and 4,721,293 dated Jan. 26, 1988.
In the first, a self-locking hydraulic clamping device includes a hydraulic piston which is notched on one side to form a compound camming surface which drivingly engages a spring loaded clamping pin moving in a bore normal to the bore in which the hydraulic piston moves, the later bore preferably extending parallel to the side of the workpiece being clamped.
In the second, the device provides a double acting piston formed with a camming surface intermediate its ends. A cylindrical clamping pin is guided within the device for movement in a direction perpendicular to the camming surface and is provided with an end surface perpendicular to such direction of movement which engages the camming surface. An output lever pivotally mounted on the device engages the clamping pin at one end and is operable to engage tooling at its other end to clamp the tooling in position. The clamping pin is cylindrical and is free to rotate about its axis so as to reduce localized wear when the device is repeatedly cycled. A spring operably positioned between the lever and the body of the device resiliently biases the lever and the clamping pin toward the release position.